Silicon chip with an integrated magnetoresistive head mounted on a slider

ABSTRACT

An MR head has its MR stripe protected from electro-static discharge (ESD) on a slider, such as titanium carbide. The MR stripe is protected by a plurality of silicon integrated circuit devices which conduct ESD-induced current from the MR stripe to a silicon chip substrate ground potential or to larger components in the MR head such as the first and second shield layers and the coil layer. In a preferred embodiment the integrated circuit devices and interconnects are constructed in a single crystal silicon chip. The silicon chip is fixedly mounted to a trailing edge of the slider and the MR head is mounted on a trailing edge of the silicon chip adjacent the integrated circuit devices. The invention includes a method of mass producing sliders by combining thin film technology for making MR heads with integrated circuit technology for making integrated circuit devices. These technologies are combined at the wafer level to ultimate completion of individual sliders. At the wafer level a silicon wafer, which contains the integrated circuit devices, is fixedly mounted to a wafer of slider material, such as titanium carbide. A plurality of rows and columns of MR heads are constructed on the silicon wafer adjacent the integrated circuit devices. The composite wafer is then diced into quadrants wherein each quadrant contains rows and columns of sliders with MR heads. Each quadrant is then diced into rows. Each row is then diced into individual sliders, each slider carrying an MR head which is ESD protected.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a slider mounted silicon chip with anintegrated electronic structure that includes a magnetoresistive (MR)sensor and associated circuitry, and more particularly to a silicon chipincluding an integrated MR head which is mounted to a trailing edge of aslider wherein the silicon chip contains integrated circuits, such aselectrostatic discharge (ESD) circuits, which serve the MR sensor of theMR head.

2. Description of the Related Art

MR sensors are commonly used as read elements in thin film magneticheads for sensing recorded signals on a magnetic medium, such as amagnetic disk. A thin film magnetic head which incorporates an MR sensoris called an MR head. An MR sensor includes a thin stripe of conductivematerial, such as Permalloy (NiFe). When a magnetic medium, such as amagnetic disk, is rotated adjacent the MR sensor, magnetic fields fromthe medium induce a response in the MR sensor causing the sensor tochange its resistance. A sense current conducted through the MR sensorchanges its magnitude proportionally to the change in resistance. Themagnitude changes are then processed by channel electronics intoplayback signals representing information stored on the magnetic medium.

A typical MR stripe is 5 microns long, 1 micron high and 200 Angstromsthick. The length and thickness of the MR stripe are exposed at asurface of an MR head while the height is buried in the head body.During construction and assembly of the MR head, the MR stripe must beprotected from electrostatic discharge (ESD). A discharge of only a fewvolts can destroy or severely damage the MR stripe. Such a discharge canoccur by contact with or close proximity to a person, plastic involvedin the fabrication, or components of a magnetic medium drive.

The prior art teaches the use of electrical elements to protect MRstripes from ESD. These elements include diodes which shunt excessivecurrent away from the MR stripe to larger conductive components in thehead via leads which are connected to the MR stripe. Such largercomponents may include shield or coil layers that form part of anintegrated MR head.

ESD protection devices (ESDD) and MR heads have been fabricated onsliders. A standard material in the industry for sliders has beentitanium carbide (TIC), also known as N58. TiC is wear resistant and iseasy to machine. However, ESD robust diodes, which are required toprotect an MR stripe from ESD, cannot be produced in TiC. Nevertheless,it is known that ESD robust diodes can be fabricated in a silicon wafer.

There is a strong felt need in the art to improve the ESD protection ofMR stripes to the level of that provided by silicon diodes withoutchanging the slider material from TiC. Two technical challenges areinvolved. One is fabrication of magnetic heads on TiC sliders with thinfilm technology and the other is the construction of protection elementson a silicon wafer by integrated circuit technology. It would bedesirable if these two technologies could be merged to provide an MRhead on a slider, such as TiC, which is protected from ESD by siliconelements. Further, it would be desirable if a method of fabricationcould be provided which combines the two technologies for mass producingMR heads on sliders with ESD protection.

SUMMARY OF THE INVENTION

The present invention provides an MR head on a slider which is protectedfrom ESD damage by silicon integrated circuit elements. This isaccomplished by locating a silicon chip, containing the circuit elementson the trailing edge of the slider. In a preferred embodiment a thinfilm MR head is located on the trailing edge of the silicon chip so thatwhen the MR head is constructed interconnects can easily be made withthe integrated circuit elements. In an alternative embodiment the MRhead is constructed on the trailing edge of the slider and the siliconchip is mounted adjacent the MR head making connection throughpre-formed pads.

A unique series of steps have been provided for mass producing the MRhead on a slider with ESD protection. Both technologies are merged atthe wafer level. Integrated circuit technology is employed to constructintegrated circuit elements for multiple MR heads on a silicon wafer. Ina preferred embodiment this silicon wafer is fixedly attached to a waferof slider material to provide a composite wafer. Using thin filmtechnology a series of MR heads are constructed on top of the siliconwafer with connections being made to the integrated circuit elements.The composite wafer is then diced into quadrants, each quadrantcontaining rows and columns of sliders. Each quadrant is then diced intorows, each row containing a row of sliders. Each row is then lappedwhich forms an air bearing surface (ABS) for each slider. Each row isthen diced into individual sliders which is the completed product.

It should be understood that integrated circuit elements includingdiodes could be constructed in the silicon wafer for use with the MRhead. Examples of other integrated circuit elements are an amplifier foramplifying a sense signal from the MR stripe, a thermistor for sensingheat buildup or an accelerometer for sensing movement of the slider forcontrol purposes.

An object of the present invention is to provide an MR head which isconnected to silicon integrated circuit elements on a slider.

Another object is to provide an MR head which is protected from ESD bysilicon integrated circuit elements on a slider which is constructed ofa material other than silicon.

A further object of the present invention is to provide an MR head whichis protected from ESD by silicon integrated circuit elements on a sliderwhich is constructed of TiC.

Yet another object is to provide a method of merging thin film andintegrated circuit technologies for mass producing MR heads on sliderswhich are protected from ESD by integrated circuit elements.

Other objects, advantages and features of the invention will be readilyapparent after reviewing the following specification, claims andaccompanying drawings.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a disk drive.

FIG. 2 is a schematic isometric cross-sectional illustration of a firstembodiment of the invention which includes an MR head mounted on asilicon chip which, in turn, is mounted on the trailing edge of aslider.

FIG. 3 is a schematic isometric illustration of the first embodiment ofthe invention which includes an MR head mounted on a silicon chip which,in turn, is mounted on the trailing edge of a slider.

FIG. 4 is a schematic planar illustration of circuit connections of anMR stripe to a pair of silicon integrated circuit elements devices.

FIGS. 5A-5C are schematic illustrations of a method of mass producingthe first embodiment of the invention shown in FIGS. 2-4.

FIG. 5A is a schematic isometric illustration of the step ofconstructing a plurality of silicon integrated circuit elements on asilicon wafer.

FIG. 5B is a schematic isometric illustration of the step of fixedlymounting the silicon wafer to a TiC wafer for constructing a pluralityof sliders.

FIG. 5C is a schematic isometric illustration of constructing rows andcolumns of MR heads on the silicon wafer.

FIG. 6A is an illustration which is the same as FIG. 5A.

FIG. 6B is a schematic isometric illustration constructing a pluralityof rows and columns of MR head on the silicon wafer before fixedlymounting the silicon wafer to the TiC wafer.

FIG. 6C is a schematic isometric illustration is the step of fixedlymounting the silicon wafer to the TiC wafer to form a composite waferafter constructing the MR heads on the silicon wafer.

FIG. 7 is a schematic illustration of the step of dicing the compositewafer into quadrants, each quadrant containing rows and columns ofsliders.

FIG. 8 is a schematic isometric illustration of one of the rows of MRheads after dicing one of the quadrants of FIG. 7 into a plurality ofrows of sliders.

FIG. 9 is a schematic isometric illustration of a single slider afterdicing the row in FIG. 8 into individual sliders.

FIG. 10 is a schematic electrical diagram of the components of an MRhead connected via a plurality of integrated circuit elements thatprovide ESD protection.

FIG. 11 is a schematic illustration of a pair of back-to-back silicondiodes.

FIG. 12 is a schematic illustration of a pair of back-to-back stackedsilicon diodes.

FIG. 13 is a schematic illustration of a pair of back to back fieldeffect transistors (FETs) or TFTs.

FIG. 14 is a schematic isometric illustration of a second embodiment ofthe present invention which includes an MR head mounted on the trailingedge of the slider between the slider and the silicon chip.

FIG. 15 is a planar schematic illustration of the connection of a pairof silicon integrated circuit elements to an MR stripe of an MR head.

FIG. 16-20 are schematic illustrations of the method of constructing thesecond embodiment of the invention shown in FIG. 14 and 15.

FIG. 16 is a schematic isometric illustration of the step ofconstructing a plurality of silicon integrated circuit elements on asilicon wafer.

FIG. 17 is a schematic isometric illustration of the step ofconstructing rows and columns of MR heads on a TiC wafer which is usedto make sliders.

FIG. 18 is a schematic isometric illustration of the step of fixedlymounting the silicon wafer to the TiC wafer to form a composite wafer.

FIG. 19 is a schematic illustration of the step of dicing the compositewafer into quadrants of rows and columns of sliders.

FIG. 20 is a schematic isometric illustration of a row of sliders aftera step of dicing one of the quadrants into a plurality of rows andcolumns of sliders.

FIG. 21 is a schematic isometric illustration of a single slider after astep of dicing the row shown in FIG. 20 into a plurality of sliders.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings wherein like reference numerals designatelike or similar parts throughout the several views, a magnetic diskdrive 30 is illustrated in FIG. 1. The drive 30 includes a spindle 32which supports and rotates a disk 34. The spindle 32 is rotated by amotor 36 which is controlled by motor controls 38. A magnetic read/writetransducer, referred to as a magnetic head 40, is mounted on a slider 42which, in turn, is supported by a suspension and actuator arm 44. Themagnetic head 40 may include or comprise an MR head according to theinvention. The suspension and actuator arm 44 positions the slider 42 sothat the magnetic head 40 is in a transducing relationship with asurface of the disk 34. When the disk 34 is rotated by the motor 36, airmoved by the top of the disk together with the structure of the slider42 causes the slider to ride on a cushion of air, referred to as an airbearing. The thickness of the air bearing, also referred to as the"flying height" of the slider, is typically less than 5.0 microinches.The magnetic head 40 is then employed for writing and readinginformation in multiple circular tracks on the surface of the disk 34.These information signals as well as servo signals for moving the sliderto various tracks are processed by drive electronics 46 which areconnected to the magnetic head 40.

FIG. 2 illustrates a first embodiment of the invention which includes anMR head 50 mounted on a trailing edge 52 of a silicon chip 54 which, inturn, is mounted on a trailing edge 56 of a slider 58. The slider 58 ispreferably constructed of titanium carbide (TIC) which is a standardmaterial in the industry for sliders. This slider material is known asN58. The silicon chip 54 is preferably single crystal silicon which willbe explained in more detail hereinafter.

The MR head 50 includes an MR stripe 60 which is sandwiched betweenfirst and second gap layers 62 and 64 which, in turn, are sandwichedbetween first and second shield layers 66 and 68. A coil layer 70 issandwiched between first and second insulation layers (not shown) which,in turn, are sandwiched between first and second pole pieces 68 and 72.The second shield layer S2 also serves as a first pole piece P1. Thistype of MR head is known in the industry as a merged MR head. The polepieces 68 and 72 terminate at an air bearing surface (ABS) 74 and firstand second pole tips 76 and 78 which are separated by a gap insulationlayer 80. A sense current is transmitted to the MR stripe 60 by a pairof conductor leads, one of the leads being illustrated at 82 in FIG. 2.A write function is performed by the MR head by the first and secondpole tips when magnetic flux bridges across the gap 80 in response tomagnetic flux induced into the first and second pole pieces 68 and 72 bythe coil layer 70. A playback function is performed by the head whenmagnetic fields on a moving medium cause a change of resistance of theMR stripe; the resistance change causes a voltage change across theleads connected to the MR stripe; voltage variations are processed intoinformation signals.

It is important that the MR stripe 60 be protected from electro-staticdischarge (ESD) during its construction and during assembly of the diskdrive shown in FIG. 1. A few volts can destroy or damage the MR stripe,rendering the read function of the MR head inoperative. The MR stripe 60can be protected from ESD by a protective element which is connected tothe MR stripe. A typical ESD protective element is a silicon diode whichshunts ESD-induced current to larger components in the head such as thefirst and second shield layers 66 and 68 and the coil layer 70. A blockdiagram for such electrical connections will be described in more detailhereinafter.

The protective element may be one or more integrated circuit elementsconstructed in the silicon chip 54, which is preferably single crystalsilicon. For example, one of a plurality of silicon diode devices isshown in the silicon chip at 84. Interconnects, one of which is shown at86, are employed to connect the protective element 84 to otherprotective elements (not shown) as well as to pads, a portion of one padbeing shown at 88, which are at the top surface of an insulation layer90. Vias, one of which is illustrated at 92, extend through the variouslayers of the MR head from various components in the head to the pads 88for electrically connecting the head components to the protectiveelements 84. Numerous vias may be provided for connecting multiplecomponents of the MR head to multiple protective elements as will beexplained in more detail hereinafter. It should be understood howeverthat the protective elements contemplated by the invention are notrestricted to silicon diodes, but may employ other silicon integratedcircuit elements such as silicon controlled rectifiers (SCRs), bipolartransistors and MOSFETS. The silicon chip 54 is fixedly mounted to thetrailing edge 56 of the slider 58. This may be accomplished by bondingwith epoxy or by C-4 solder. In actual practice an overcoat (not shown)is deposited over the second pole piece 72 to complete the MR head. TheMR head and the silicon chip then form a small portion of an air bearingsurface (ABS). The major portion of the air bearing surface is providedby the slider 58.

FIG. 3 is an illustration of the first embodiment 100 constructedaccording to the teachings of FIG. 2 with the MR head shownschematically mounted on the trailing edge 56 of the silicon chip 54which, in turn, is mounted on the trailing edge 56 of the slider 58. TheABS, which is shown at 74, is formed by the bottom surface of the MRhead, the silicon chip 54 and the slider 58. While the descriptiondescribes a single MR head carried by the slider, it should beunderstood that the slider may carry a plurality of MR heads accordingto the teachings of the present invention. FIG. 4 is an exemplaryillustration of a pair of silicon protective devices 84 interconnectingthe MR stripe 60 to larger head components 102 via pads 88 and via MRhead vias 92.

A method of constructing the first embodiment illustrated in FIGS. 2through 4 is illustrated in a series of steps shown in FIGS. 5A through9. In FIG. 5A the first step is to construct a plurality of protectiveelements using known techniques for integrated circuit fabrication onone face of a silicon wafer 104. Such elements may include silicondiodes. The next step is to fixedly mount the silicon wafer 104 on awafer 106 of slider material, such as TiC. The next step is to constructrows and columns of MR heads 50 on top of the silicon wafer and on topof the protective silicon devices 84 as described hereinabove withreference to FIG. 2. This provides a composite TiC/Si composite wafer.

Modified steps in the construction are illustrated in FIGS. 6A through6C for achieving the composite wafer shown in FIG. 5C. The step shown inFIG. 6A is the same as the step implemented in FIG. 5A, namely,constructing the protective silicon devices 84 on the silicon chip 104.FIG. 6B is different in that the magnetic heads 50 are constructed onthe silicon chip prior to fixedly mounting the silicon chip on the TiCwafer 106. In FIG. 6 the silicon wafer 104 of FIG. 6B is fixedly mountedto the TiC wafer 106 providing the same result as shown in FIG. 5C.

FIG. 7 illustrates a step of dicing the composite wafer of FIG. 5C orFIG. 6C into quadrants, each quadrant containing rows and columns ofmagnetic heads 50. FIG. 8 illustrates one row of sliders 110 after oneof the quadrants 108 in FIG. 7 is diced into a plurality of rows 110 ofsliders. FIG. 9 illustrates a composite single slider 58, silicon chip54, and magnetic head 50 after dicing the row of sliders 110 in FIG. 8into a plurality of sliders.

FIG. 10 is a schematic block diagram of exemplary electrical connectionsof ESD diodes (ESDD) for shunting ESD-induced current from the MR stripe60 to the larger components of the MR head such as the first and secondshield layers 66 and 68 and the coil layer 70. The ESD induced currentcan also be shunted to a silicon chip substrate or ground potential.Suitable ESDDs are illustrated in FIGS. 11 through 13. In FIG. 11 a pairof back-to-back silicon diodes with each leg of opposite polarity areprovided so that currents of either plus or minus polarity can beconducted therethrough. It is important that the ESDDs only shuntcurrents which exceed an operational sense level for the MR stripe. Inorder to accomplish this purpose, a series of diodes may be employed ineach leg of the protective element as illustrated in FIG. 12. The morediodes located in each leg, the higher the voltage that will be requiredto cause the leg to operate and conduct current. Still another ESDD isillustrated in FIG. 13 which employs a pair of field effect transistors(FETs or TFTs) which can be selectively adjusted for each leg of theprotective element.

FIG. 14 illustrates a second embodiment of the invention wherein the MRhead is constructed on the trailing edge 56 of the slider 58. In thisarrangement the MR head is located between the slider 58 and the siliconchip 54. FIG. 15 illustrates an exemplary connection of the MR stripe 60to larger components 102 in the head. In this embodiment the MR stripe60 is connected by vias 92 to a pair of pads 120 at an outer surface ofthe head for connection to corresponding pads 88 at an outer surface ofthe silicon chip. The pads 120 and 88 connect with one another when thesilicon chip 54 is mounted over the MR head on the slider 58.Accordingly, the MR stripe 60 is connected to the larger head components102 via the head vias 92, the pads 120 and 88 and the protectiveelements 84.

FIGS. 16 through 21 illustrate the various steps in constructing thesecond embodiment illustrated in FIGS. 14 and 15. FIG. 16 illustratesthe step of constructing the protective elements on the silicon wafer122. FIG. 17 illustrates the step of constructing the MR heads on theTiC wafer 124. FIG. 18 illustrates the step of fixedly mounting thesilicon wafer 122 to the TiC wafer 124. FIG. 19 illustrates dicing thecomposite wafer of FIG. 18 into quadrants 130 which contain rows andcolumns of the desired sliders. FIG. 20 illustrates a row of desiredsliders after a step of dicing one of the quadrants 130 of FIG. 19 intoa plurality of rows of sliders. FIG. 21 illustrates a composite slider,MR head, and silicon chip 134 after dicing the row of slider 132 into aplurality of individual sliders. One advantage of this method over themethod illustrated in FIGS. 5A-9 is that the heat in constructing the MRheads on the wafer 124 will not damage the bonding of the wafer 122 to124 as illustrated in FIG. 18.

Obviously, other embodiments and modifications of the invention willoccur to those of ordinary skill in the art in view of the aboveteachings. Therefore, the invention is to be limited only by thefollowing claims, which include all of such embodiments andmodifications when viewed in conjunction with the above specificationand accompanying drawings.

We claim:
 1. A combined head and slider comprising:a non-silicon sliderbody having a trailing edge; a silicon chip having a leading edge and atrailing edge; the leading edge of the silicon chip being fixedlymounted to the trailing edge of the slider: at least one silicon circuitdevice mounted in the silicon chip; the head being mounted on a selectedone of the trailing edge of the slider between the slider and thesilicon chip or the trailing edge of the silicon chip and beingconnected to the silicon circuit device.
 2. A combined head and slideras claimed in claim 1 including:the slider body being TiC.
 3. A combinedhead and slider as claimed in claim 1 including:the head being mountedon the trailing edge of the slider.
 4. A combined head and slider asclaimed in claim 1 including:first and second threshold conductivedevices of opposite polarity comprising first and second silicon circuitdevices respectively.
 5. A combined head and slider as claimed in claim4 including:the head being an MR head with an MR stripe; the MR stripebeing sandwiched between first and second gap layers, the first andsecond gap layers being sandwiched between first and second shieldlayers, a coil layer sandwiched between first and second insulationlayers and the insulation layers being sandwiched between first andsecond pole pieces; and first and second ends of the MR stripe beingconnected to at least one of the first and second shield layers or thecoil layer via the first and second threshold conductive devicesrespectively.
 6. A combined head and slider as claimed in claim 5including:the head being mounted on the trailing edge of the siliconchip.
 7. A combined head and slider as claimed in claim 6 including:theslider body being TiC.
 8. A combined head and slider as claimed in claim7 including:first and second threshold conductive devices of oppositepolarity comprising first and second silicon circuit devicesrespectively.
 9. A combined head and slider as claimed in claim 8including:the head being an MR head with an MR stripe; the MR stripebeing sandwiched between first and second gap layers, the first andsecond gap layers being sandwiched between first and second shieldlayers, a coil layer sandwiched between first and second insulationlayers and the insulation layers being sandwiched between first andsecond pole pieces; and first and second ends of the MR stripe beingconnected to at least one of the first and second shield layers or thecoil layer via the first and second threshold conductive devicesrespectively.
 10. A combined head and slider as claimed in claim 9comprising:the head having first and second interconnects which areconnected to said at least one of the first and second shield layers orthe coil layer; the silicon chip having first and second interconnectswhich are connected to said first and second threshold conductivedevices respectively; and the first and second interconnects of the headbeing connected to the first and second interconnects of the siliconchip.
 11. A combined MR head and slider as claimed in claim 9including:each threshold conductive device being a back to back silicondiode.
 12. A combined MR head and slider as claimed in claim 9including:each threshold conductive device being a back to backtransistor.
 13. A combined head and slider as claimed in claim 10including:the head being mounted on the trailing edge of the siliconchip.
 14. A combined head and slider as claimed in claim 13including:the slider body being TiC.